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6D30.10 - Newton's Rings

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​6D30.10 - Newton's Rings

Title6D30.10 - Newton's Rings

Demonstrate Newton's rings.

Assembly Instructions


The students see an image from the reflected light off the Newton's rings surface. To focus that image, we use a large, focusing lens. The light source is a 35mm projector with a circular aperture in it.
Direct the light onto the surface. Make sure the reflected light is visible on the wall (it should be circular, but out of focus).
Next, put the focusing lens in the path of the reflected light. First do this manually to roughly get the plane where the lens focus's the light. Then, put the lens in a stand and fix it in place so the image is in focus.
Turn off the room lights and make sure the image is visible.

Setup Time15
Operation Time
Preview Time5
Operation Instructions

A concave lens is fixed against a glass plate in a special fixture which is mounted on a stand. The resulting reflected fringe pattern is projected on the side screen for the whole class to see. The face of the fixture is strongly illuminated with the light from the slide projector. The fixture is adjusted so that the bright spot from the reflection is on the side screen. Then a short focal length lens is inserted in the path so as to produce an image on the screen.

Demo on DimeNo
PIRA 200Yes
Export Instructions (if different)

The physical intersection between a slightly convex lens and a flat surface produces interesting interference patterns. The reflected light's wavelength is determined by the separation between the surfaces, and since this varies slowly we observe the spectrum of the rainbow with increasing radius.
Analysis Links
Giant Newton's rings: Kai-yin Cheung and Se-yuen Mak, Phys. Teach. 34, 35 (1996)

Category6 Optics
Subcategory6D - Interference
Construction Information
projector slit - small circular
Newton's Rings - concave lens/glass plate assembly
lens - convex 3.5" diameter, mounted on tripod